Backyard Aquaponics
A place to discuss aquaponics

Hello I am new to this, so please be patient. I created an aquaponics system with our swimming pool 50,000ltrs. The pool has been used for 2 yrs to breed 9 varieties of local frogs, but with a long term aim of growing fish. So when I came across aquaponics I become quite excited at the concept. I created 3 grow beds from some troughs 1.7mts dia 400mm deep (gravel depth). I used washed white quartz gravel. I planted many of the vegies and about 3 weeks later added 100 Silver Perch. I flood each growbed to within 10mm of the surface 20 times a day, this water is released slowly over 40 minutes to a depth of about 200mm The fish are thriving, after about 9 weeks some of the fish would be up to 130mm in size. But the vegies are just not growing or growing very slowly. When I tested the PH (at the start) it was 7.1. At the moment the water is being drawn from near the surface so the heavies are remaining on the bottom. I have ordered a test kit, but wondered if anybody has any suggestions as to why I have such poor plant growth. Ambient daytime temperatures 25c to 35c.
Thanks, Alan

I'd say too much water not enough nutrient.. Any nutrient in the water will be very dilute for a start and also consumed by algae in the water and on the sides of the pool pretty quickly.

I agree.

I would also recommend dropping the max flooded water levels in the GB's to about 40mm from the surface, otherwise you'll have lots of algae growth (once you manage to increase your nutrient levels) and excessive evaporation.

With 36cm of flooded gravel in the beds you'd have a total wet gravel volume across the three beds of about 2500L. At a safe stocking density of 20L per Silver perch (25L for Trout or Barra) you could stock 125 SP's... still not enough fish to provide an adequate nutrient level in 50,000L of water IMO... You need a lot more gravel GB's and more fish.

In the meantime I would get a 1L bottle of Seasol and tip the entire contents into the pool.

PJL may be able to add his experiences here for you. I think he ran his big tank unfiltered for over a year so it gives you an idea what is level of biofiltration occurs just within the tank itself.

He now has added grow beds so this thread may help you.

viewtopic.php?f=18&t=12883&hilit=concrete

Thanks for that, I thought that might be the problem. To make matters worse I have a few water plants in the pond (which are growing very well). I have been using Seasol but not in that quantity.

there you go.. the water plants will consume lots of nutrients as well...

Thats a big pool! what is it made from?

Also, is your pool covered? If not, I would suggest covering most of the pool to impede the growth of algea since it not only requires sunlight, but also consumes nutrients the plants need to survive.